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a small Rorqual. But even these are larger than the majority
of Toothed Whales.

The most characteristic feature by which the Whalebone
Whales are to be distinguished from other Whales is that which
gives to them their name, the presence of whalebone. Whale-
bone is a horny product of the epithelium lining the mouth, and
is comparable to an exaggeration of the transverse ridges which

are found in the mouths of all
mammals upon the palate. In
non - Cetacean mammals these
ridges vary in depth, and are
arranged as a rale transversely,
but with an oblique inclination.
This is precisely how the plates
of baleen are disposed in the
mouth of a Whale. Each piece
of " bone " is triangular in shape,
the broader end being that of
attachment while it narrows
gradually; the inner side of the
blades is frayed out into a number
of threads which form the strain-
ing apparatus. The plates vary
in length up to as great an ex-
treme length as 13 feet, which
occurs in the Eight Whale at
TO ion a *• *          -         ^ times. The colour is black or

PIG.   189,—Section   of  tipper jaw,   with         ,                       _ .           _,               ,

baleen plates, of Baiaenoptera.   a,  paler, even white.     The number

Bone  of jaw;   b   gum;   c, straight      f   t}            lateg  in   the   mouth   IS

edge of baleen   plate ;   d,  e,  frayed                     *                                       .   .

out surface of baleen plates.   (After very   great.     As   many   as   370
Owen->                                            blades have been counted.    They

diminish in length towards both ends of the series. Though
whalebone has been in use for a long period, whence the whale-
bone came was formerly one of those -things not generally

A very prevalent notion was that the whalebone formed the
eyelids or perhaps the eyelashes of the creature. Sealiger, com-
menting upon Aristotle, held that the whale had " lamellae upon
the eyebrows, which, when the head is plunged below the surface,
were raised by the water; but when the animal raised its liead